An atom contains 20 protons, 20 neutrons and 20 electrons. A proton and a neutron each have relative mass 1. An electron has relative mass 11840\displaystyle \frac{1}{1840}18401.
Approximately what percentage of the atom's mass is outside its nucleus?
33%33\%33%
0.054%0.054\%0.054%
0.027%0.027\%0.027%
2.7%2.7\%2.7%